HELP--The Leaves on My Trees are Turning Yellow!!!!
Gail Ruhl, Senior Plant Disease Diagnostician,
Director, Botany & Plant Pathology
The diagnostic lab has received numerous
samples and phone calls regarding yellowing of foliage on a
variety of trees, including pin oak, red maple, sweet gum and
Yellowing of foliage (chlorosis) is due to
a lack of chlorophyll development. Compacted soils, poor
drainage, alkaline soils, nutrient deficiencies, and root damage
are among the factors that can induce chlorosis in woody plants.
Pin oak, riverbirch and red maple are sensitive to soil conditions
such as high pH, which ties up manganese and iron as well as
other minor elements, making them unavailable to the roots. Poorly
drained or compacted soil can also have these effects by resulting
in poor root growth and inability to take up these minor elements.
This problem often occurs under the stressful conditions of summer
when roots are unable to take up enough manganese or iron to
support continuing growth.
What to do? Recommendations vary. Pin Oak and Riverbirch often
exhibit classic symptoms of iron deficiency while Red Maple often
exhibits classic symptoms of manganese deficiency. Some suggest
spraying the foliage with a mixture of iron and manganese sulfates
or chelates (1 1/2 tablespoons each per gallon of water). This
should correct the problem in a week or so, but unfortunately
it is temporary in effect. Applying the two minor elements to
separate branches will allow you to determine which one or perhaps
both are the problem. The following extension publications provide
more details on approaches to this problem which involve correcting
poor drainage or high pH, and the application of minor elements
by several techniques:
Chlorosis of Trees and Shrubs - Purdue University Extension
Chlorosis Of Woody Plants: Cause And Control - University
of Illinois Extension (pdf file)
on Plant Diseases: Chlorosis - University of Illinois Extension
and Treating Iron Chlorosis in Trees and Shrubs - Utah
Chlorosis in Trees - Kansas State University Extension
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